Construction for the tap holes of open-hearth furnaces



April 20, 1954 F. H. LOFTUS ETAL 2,676,011

CONSTRUCTION FOR THE TAP HOLES OF OPEN-HEARTH FURNACES Filed Jan. 28,1950 2 Sheets-Sheet 1 INVENTORS FRED A. LOFTUS MD BY VINCENT Q- noa uoueApril 20, 1954 F. H. LOFTUS ET AL 2,676,011

CONSTRUCTION FOR THE TAP HOLES OF OPEN-HEARTH FURNACES Filed Jan. 28,1950 2 Sheets-Sheet 2 INVENTOR FlED H. LOFIUS L BY VINCENT IL TEOGLIONE-Patented Apr. 20, 1954 CONSTRUCTION F OR THE TAP HOLES OF OPEN-HEARTHFURNACES Fred H. Loftus, Mount Lebanon, and Vincent R. Troglione,Wilkinsburg, Pa., assignors to Loftus Engineering Corporation, acorporation of Maryland Application January 28, 1950, Serial No. 141,024

6 Claims- 1 This invention relates to metallurgical furnaces,particularly to furnaces for melting and refining metal and metalliccompositions, such furnaces as the open hearths employed in theproduction of steel. The invention consists in certain new and usefulimprovements in furnace construction at and below the outlet end of thetap hole of the furnace.

An. open hearth furnace consists of a chamber having a hearth, sidewalls, end walls and roof constructed of refractory material, supportedand externally reinforced and tied by means of a steel framework. Thehearth of the furnace is dished, providing a basin that sustains thecharge of metal and ingredients required to produce a specified heat ofsteel. At the two ends of the furnace ports are provided, and duringfurnace operation fuel and air are admitted through the port at one endof the furnace, whereby flames and hot gases are projected across thehearth to supply the required heat to the furnace charge. The hot gasesor products of combustion exit through the port at the opposite end ofthe furnace. From time to time the furnace is reversed; that is to say,the port which had been serving as the firing port becomes the outgoport, and the port which had been serving as the outgo port becomes thefiring port. And so the operation of the furnace is continued, slagbeing flushed off and required materials added to the charge. Afterseveral hours of operation the metallic charge is reduced to desiredanalysis, whereupon the heat is tapped.

For purposes of tapping the metal, a hole opens laterally through thebody of the furnace hearth, and this holecalled the tap hole-is normallyclosed and sealed by means of a stopper formed of refractory material.In order to tap a heat this stopper is opened or drilled through, andthe molten metal flows outwardly from the hearth to an inclined spoutleading from the outlet end of the tap hole to a ladle or otherreceptacle.

The inclined spout consists of a refractory.- lined chute, upon whichthe stream of molten metal emerging from the tap hole flows to theladle. The spout is detachably joined to the furnace structure at theoutlet end of the tap hole, and in the course of service the refractorylining of the spout becomes worn. For this reason one or more standbyspouts are provided, whereby a spout whose lining has become worn inservice may be readily removed and a new one substituted.

It has been found in the operation of open hearth furnaces that moltensteel tends to escape in small quantities through the joint between thespout and the furnace structure at the outlet end of the tap hole.Furthermore, the refractory structure adjacent to the outlet end of thetap hole suffers under the extreme heat to which it is subjected, andfrequently small avenues of escape develop, with the effect that, duringthe tapping of a heat, molten metal seeps downwardly and drips uponcertain parts of the structural steelwork that supports the furnace. Themolten metal, thus draining upon the steel-work, over a period of timecuts through the steel and weakens the basal structure of the furnace.

In the normal operation of an open hearth furnace it is necessary tomake bottom after the tapping of each heat. Making bottom consists offilling in the holes or recesses worn in the hearth of the furnace bythe erosive action of the molten metal. These holes or recesses arefilled-in with particulate refractory material which, under the heat ofthe furnace, becomes fused into place, restoring the surface of thehearth to substantially normal contour. Sometimes the recesses appearingin the furnace hearth are located in such positions that all of themolten metal will not drain from the furnace when it is tapped. Whenthis occurs the tapping spout is removed, and the residual pool ofmolten metal is blown by an air jet into the tap hole; sometimes themetal cannot be entirely removed in this way and it is necessary to formin the hearth a groove leading from the residual pool of metal to theupper end of the tap hole, whereby the residual metal may drain from thefurnace. In either case the residual molten metal is caused to flow intothe tap hole, whence it spills from the outer end of the tap hole andsolidifies upon the parts of the furnace structure located therebelow,forming a solid scab of steelknown in the art as a monkey.

It will be understood that the residual metal thus removed from thefurnace, while being sufficiently molten to run through the tap hole,does not have the temperature nor the heat content of the main body ofmolten steel which was tapped from the furnace, and it is for thisreason that the residual metal solidifies quickly and forms a monkey. Itis more practical to allow this metal to solidify on the furnacestructure beneath the tap hole, as described, where it can be pulledaway by means of the usual overhead crane, than to permit it to solidifyin the spout. It is far more costly to remove solidified metal from thespout and make the spout repairs necessary than to remove a monkey fromthe furnace structure immediately below the tap hole outlet. However,the removal of monkeys is an objectionable incident to furnaceoperation, since the solidified metal sometimes freezes and anchors tothe steel-work of the furnace body, requiring considerable time toeffect its removalsometimes with injury to the furnace steel-work.

The major object of my invention is two-fold:

(1) To protect the steel-work of the furnace from the deleteriouseffects of molten metal that drains through the joint between the taphole and the spout.

(2) To facilitate the removal of monkeys and to minimize damage to thefurnace structure while so doing.

The invention will be understood upon reference to the accompanyingdrawings, in which Fig. 1 is a view of the central body portion of anopen hearth furnace through which the tap hole opens, the view beingfragmentary and illustrating the structure partly in side elevation andpartly on the section planes indicated at 1-1 in Fig. 2;

Fig. 2 is a fragmentary sectional view of the furnace, as seen on avertical plane extending through the axis of the tap hole, the sectionplane being indicated at II-II in Fig. l; and

Fig. 3 is a detailed view of the device in which our present inventionis centered, the illustration being a horizontal section on the planeindicated at III-III in Fig. 2.

In view of the general description presented in the preamble of thisspecification, it is considered needless to illustrate and describe thecomplete structure of an open hearth furnace. The invention will bereadily understood upon reference to the fragmentary illustrationspresented.

Referring to the drawings, the reference numeral 2 indicates therefractory backwall and 3 the refractory hearth of an open hearthfurnace of conventional construction. The furnace structure is borneupon and contained within a steel framework comprising horizontal hearthbeams 5, overlaid with a pan 5 formed of heavy steel plate, upon whichthe insulation and refractory body of the furnace hearth is supported.The hearth beams 6 are supported on heavy concrete piers that are spacedfrom the opposite sides of the tap hole 4, which is located on thetransverse center line of the furnace and extends through the refractorybody of the furnace hearth. The concrete piers do not appear in thedrawings, but may be conventional in arrangement and construction. Anopen hearth furnace of the construction specified herein is known in theart to be of pan-type construction.

The walls of the furnace (the conventional sloping backwall only beingshown herein), are laterally supported and reinforced by means ofbuckstays 8 and cast steel or iron breast plates 9 and I2. The front andback buckstays are securely anchored at their lower ends to the frontand back edges of the basal structure of t. e furnace, and at theirupper ends the buckstays of the backwall are cross-connected to theupper ends of the buckstays of the front wall (not shown) of thefurnace.

Extending outwardly and downwardly from the outlet end of the tap hole 4is a, spout iii. This spout comprises a trough formed of cast ferrousmetal, which is lined with refractory material II. The breast plate 12,through which the tap hole 4 opens, includes on each side of the outletend of the tap hole an integral, vertically extending web or flange l3which is notched at Hi. On each side of the spout a pin or boss I5 isintegrally formed, and these pins or bosses are seated in the notchesHi, thereby removably securing the upper end of the spout to the furnacestructure, with the refractory-lined trough of the spout joined, as atIS, with the outlet end of the tap hole 4. The lower end of the spoutmay be vertically supported in conventional manner, upon the usualplatform or by means of an overhead hanger (not shown). As thusorganized the spout may be readily removed and replaced as need be.

In open hearth furnaces as heretofore constructed, it is at the joint itwhere a seepage of molten metal develops during the repeated tapping ofthe furnace in operation. A fissure or crack opens downwardly throughthe refractory material installed at 20 beneath this joint, and, duringeach tapping of the furnace, molten metal drains through the fissureupon the steel pan 5 and hearth beams 6 below. The molten metal, thusdraining and dripping downwardly, cuts through the steel pan and hearthbeams below the joint 18. The furnace structure is thus wounded, and thewound is located at the middle of the span of the furnace-supportingbeams between the piers, where a diminution in structural strength isparticularly objectionable.

The removal of monkeys from the wounded furnace structure is not onlyrendered more difficult, but the damage to the structure is aggravated.

In the elimination of these objections, the furnace structure of thisinvention is fashioned to provide for the clear fall of the drainingmolten metal to the pit beneath the furnace, where it does no harm andcan be removed when it is convenient to do so. The means embodied in thefurnace structure to this end may be termed a base-protecting device.

More specifically, the two hearth beams ta, which in prior furnacesextend without interruption between the supporting piers, arediscontinued for an interval beneath the outlet end of the tap hole, andmeans are provided for integrating the end of the beams at suchinterval, to afford a steelwork construction that is amply sturdy, whileproviding a vertical passage for an unobjectionable drainage of moltenmetal into the pit.

Such means consist in what is termed a splashplate, comprising astructural casting, preferably of iron or steel, of the approximatelyC-shape appearing in horizontal section in Fig. 3. The casting includestwo side flanges or webs 22, between which inwardly extends a heavy web22 of approximately semi-circular or C-shaped body substantiallyembraces a vertical line extending downwardly from the outlet end it ofthe tap hole as viewed in plan. This web 22 extends vertically intransverse or vertical section (see Fig. 2), and is provided with twosets of vertical reinforcing flanges 23 and 24, and two set ofhorizontal reinforcing flanges 25, 26 and 27. In Fig. 3 the ends of thetwo beams ta which are interrupted in extent beneath the outlet of thetap hole 4, have their medial webs 6b continued beyond the basal flanges60 to receive in bolted union two steel angles 28. The adjacent hearthbeam 6, whose extent is continuous beneath the furnace, carries twoheavy transverse steel plates 28, to which the angles 28 at the ends ofthe beam 611 are welded. The plates 29 are spaced to receive snuglybetween them the structural casting 2 !-2:i, and such casting issecurely assembled in the structure, by means of bolts 39 shown in Fig.3. The plates 29 are in and of themselves a very sturdy structure, butthey nonetheless are reinforced by mean of paired angles 3i, bolted tothe vertical web of the adjacent hearth beam t. Over the ends of thediscontinued beams 6a a heavy structural channel 32 is welded to theface of each plate 29, providing not only reinforcement for the plate,but a sturdy seat upon which the angle-reinforced ends of the beams 5amay bear, whereby all of the load on the beams need not be carriedsolely by the welded unions of such ends of the beams dc to the plates29. In the case of large furnaces, or furnaces built with extra heavysteel-work, the plates 29 may be dispensed with, and the channels 32 maybe united to the beam 6 (Fig. 3). The vertical webs of these channelsmay be bolted or welded to the ends of beams to and to the fianges 25 cfthe structural casting 24-27.

referring particularly to Fig. 2, it will be noted that the arcuate web22 of the structural casting carries at its upper and lower edgeshorizontal flanges 33 and 34 which are integrally united at their endsto the vertical webs 23. In the arcuate channel thu formed by andbetween the flanges 23, 33 and 34, and the arcuate web 22, a heavylining or facing 35 of refractory brick is installed. This structureeliminates the objections alluded to, and affords reinforcement of thefurnace steel-work, and many other advantages. It may be noted that thepan plate 5 of the furnace is out out above the structural casting2i--2'I, so that metal draining from the joint iii and through the body29 of refractory material may readily drop into the pit beneath thefurnace. For purposes of supporting the refractory material 28 when itis initially installed, a small plate at is installed, as shown in Fig.2. This plate may be readily renewed when it is desired to repair orreplace the refractory material (20) beneath the outlet end of the taphole.

It will be noted that the structural casting inserted, as illustratedand described, in the furnace structure is horizontally recessed orlaterally inset beneath the outlet of the tap hole, to the end that anymetal seeping from the joint [6, or draining from the outlet end of thetap hole when the spout It is removed for cleaning the hearth of thefurnace while making bottom, has a clear fall to the pit beneath thefurnace. Such small quantities of molten metal as may possibly adhere tothe structure beneath the tap hole will soldify upon the refractoryfacing 35. If during a prolonged period of furnace operation a heavyscab of solid metal should build up upon the refractory facing or shield35, it may readily be torn away by means of the usual overhead crane,possibly taking the refractory facing 35 with it. This presents noserious objection in operation, since the refractory facin can bereadily renewed without unduly delaying furnace production.

While the invention has been described as it is particularly adapted toopen hearth furnaces, it will be understood that the structure of theinvention may be employed in other types of metal melting and refiningequipment. It will further be understood that within the spirit of theinvention defined in the appended claims, many variations andmodifications are held in contemplation.

We claim:

1. In an open hearth furnace of pan-type construction, a furnace bodyhaving a dished hearth of refractory material laterally supported bybreast plates and vertically supported upon a structural steel basecomprising an assembly of steel hearth beams that extend longitudinallybeneath the furnace body, a tap-hole for molten steel opening laterallythrough the hearth structure and terminating in an outlet located abovesuch of said hearth beams as are positioned immediately below saidbreast plates, and piers spaced from the opposite sides of said tap-holefor the support of said structural steel base; the improvements hereindescribed wherein the hearth beams located below said breast plates areof interrupted extent in the region below the outlet of said tap-hole, asplash-plate comprising a metal body incorporated in the steel base atsaid region of interruption in the extent of the hearth beams, the metalbody of said splashplate having a recess which is of general 0 shape asviewed in a horizontal plane and extends inwardly beneath said breastplates into position vertically below said tap-hole outlet, to providefor the vertical drainage of molten steel leaking from said tap-holeoutlet in the region of said interruption in the extent of the hearthbeams.

2. In an open hearth furnace of pan-type construction, a furnace bodyhaving a dished hearth of refractory material laterally supported bybreast plates and vertically supported upon a structural steel basecomprising an assembly of steel hearth beams that extend longitudinallybeneath the furnace body, a tap-hole for molten steel opening laterallythrough the hearth structure and terminating in an outlet located abovesuch of said hearth beams as are positioned immediately below saidbreast plates, and piers spaced from the opposite sides of said tap-holefor the support of said structural steel base; the improvements hereindescribed wherein the hearth beams located below said breast plates areof interrupted extent in the region below the outlet of said tap-hole, asplash-plate comprising a metal body incorporated in the steel base atsaid region of interruption in the extent of the hearth beams, the metalbody of said splash-plate having a recess which is of general 0 shape asviewed in a horizontal plane and extend inwardly beneath said breastplates into position vertically below said tap-hole outlet, and avertically disposed facing of refractory material extending along theedge of said recess in the splash-plate body, such refractory facedrecess providing for the vertical drainage of molten steel leaking fromsaid tap-hole outlet without prohibitive damage to said hearth beamswhile permitting the ready removal of a monkey of metal accumulating onthe splash-plate body.

3. In an open hearth furnace of pan-type construction, a furnace bodyhaving a dished hearth of refractory material laterally supported bybreast plates and vertically supported upon a structural steel basecomprising an assembly of steel hearth beams that extend longitudinallybeneath the furnace body, a tap-hole for molten steel opening laterallythrough the hearth structure and terminating in an outlet located abovesuch of said hearth beams as are positioned immediately below saidbreast plates, a, tapping spout removably mounted at the outlet of saidtap-hole in a joint located above said last mentioned hearth beams, andpiers spaced from the opposite sides of said tap-hole for the support ofthe structural steel base; the improvements herein described wherein thehearth beams located below said breast plates are of interrupted extentin the region below said joint, a splashplate comprising a metal bodyincorporated in the steel base at said region of interruption in theextent of the hearth beams, the metal body of said splash-plate having arecess which is of general shape as viewed in a horizontal plane andextends inwardly beneath said breast plates into position verticallybelow said joint, to provide for the vertical drainage of molten steelleaking from said tap-hole outlet through said joint.

4. In an open hearth furnace of pan-type construction, a furnace bodyhaving a dished hearth of refractory material laterally supported bybreast plates and vertically supported upon a structural steel basecomprising an assembly of steel hearth beams that extend longitudinallybeneath the furnace body, a tap-hole for molten steel opening laterallythrough the hearth structure and terminating in an outlet located abovesuch of said hearth beams as are positioned immediately below saidbreast plates, a tapping spout removably mounted at the outlet of saidtap-hole in a joint located above said last mentioned hearth beams, andpiers spaced from the opposite sides of said tap-hole for the support ofthe structural steel base; the improvements herein described wherein thehearth beams located below said breast plates are of interrupted extentin the region below said joint,

through said joint without prohibitive damage to said hearth beams whilepermitting the ready removal of a monkey of metal accumulatin on thesplash-plate body.

5. In an open hearth furnace the combination of a horizontal pan-typestructural steel base portion of such furnace beneath an outlet end of atap-hole thereof, a splash-plate comprising a vertically extending metalbody of general 0- shape in horizontal section, and means for unitingsaid body in the furnace base portion be neath said tap-hole with saidC-shaped body of the splash-plate positioned substantially to embrace avertical line extending downwardly from said outlet end of the tap-holeand with the open side of the c directed outwardly from said baseportion, said means comprising at back and closed side of the C a pairof vertical webs that extend rearwardly, one from each end of the metalbody of the C, for rigid integration with the said horizontal structuralsteel base portion.

6. In a claim as in claim 5 wherein said splashplate carries upon theconcave face of its vertically extending C-shaped body horizontal andvertical refractory-supporting members.

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